This document provides an overview of screws, fasteners, and nonpermanent joints. It discusses different types of joints including screw joints, which are widely used for fastening and power transmission. Various screw terminologies are defined, including thread standards and diameters. The mechanics and stresses involved in power screws are analyzed. Examples of power screws like jack screws and lead screws are provided. Design of bolted joints and selection of bolts, nuts, and fasteners are also covered.
The following presentation consists of a brief introduction to power screw that we use in our day to day life, its types, analysis of load, efficiency, application and examples with images.
DME: numerical of design of bolt, punch and standard sizes of shaftsGaurav Mistry
Numerical of Bolt design, punch design and standard sizes and speed of shaft. Different stresses acting on bolt and punch. Failure of bolt and punch under stresses. Standardization, Preferred numbers, Basic and derived series.
NOTE: In the numerical no 1 of punching on slide no 10. The Answer of shear force is obtained considering thickness of plate = 5 mm. (If 6 mm is considered than the answer according to formula will be 395,841 N)
Unit 6- spur gears, Kinematics of machines of VTU Syllabus prepared by Hareesha N Gowda, Asst. Prof, Dayananda Sagar College of Engg, Blore. Please write to hareeshang@gmail.com for suggestions and criticisms.
Design against fluctuating loads, stress concentration, Goodman and Modified Goodman Diagrams, Factors affecting stress concentration, Use of charts for finding stress concentration facotrs
Spring Design, Helical Springs, compression & Extension springs, spring design procedure leaf spring, multi-leaf springs design process and analysis, Role of Spring index in spring design. Springs for Fluctuating loads.
The following presentation consists of a brief introduction to power screw that we use in our day to day life, its types, analysis of load, efficiency, application and examples with images.
DME: numerical of design of bolt, punch and standard sizes of shaftsGaurav Mistry
Numerical of Bolt design, punch design and standard sizes and speed of shaft. Different stresses acting on bolt and punch. Failure of bolt and punch under stresses. Standardization, Preferred numbers, Basic and derived series.
NOTE: In the numerical no 1 of punching on slide no 10. The Answer of shear force is obtained considering thickness of plate = 5 mm. (If 6 mm is considered than the answer according to formula will be 395,841 N)
Unit 6- spur gears, Kinematics of machines of VTU Syllabus prepared by Hareesha N Gowda, Asst. Prof, Dayananda Sagar College of Engg, Blore. Please write to hareeshang@gmail.com for suggestions and criticisms.
Design against fluctuating loads, stress concentration, Goodman and Modified Goodman Diagrams, Factors affecting stress concentration, Use of charts for finding stress concentration facotrs
Spring Design, Helical Springs, compression & Extension springs, spring design procedure leaf spring, multi-leaf springs design process and analysis, Role of Spring index in spring design. Springs for Fluctuating loads.
Basic types of screw fasteners, Bolts of uniform
strength, I.S.O. Metric screw threads, Bolts under
tension, eccentrically loaded bolted joint in shear,
Eccentric load perpendicular and parallel to axis of
bolt, Eccentric load on circular base, design of Turn
Buckle.
ME 312 Mechanical Machine Design is the flagship course of the mechanical engineering department at DHA Suffa University. This lecture is about mechanical fasteners and non-permanent joints. The course is offered every fall by Dr. Bilal A. Siddiqui.
,
diploma mechanical engineering
,
mechanical engineering
,
machine design
,
design of machine elements
,
knuckle joint
,
failures of knuckle joint under different streses
,
fork end
,
single eye end
,
knuckle pin
Springs - DESIGN OF MACHINE ELEMENTS-IIDr. L K Bhagi
Introduction to springs, Types and terminology of springs, Stress and deflection equations, Series and parallel connection, Design of helical springs, Design against fluctuating load, Concentric springs, Helical torsion springs, Spiral springs, Multi-leaf springs, Optimum design of helical spring
Basic types of screw fasteners, Bolts of uniform
strength, I.S.O. Metric screw threads, Bolts under
tension, eccentrically loaded bolted joint in shear,
Eccentric load perpendicular and parallel to axis of
bolt, Eccentric load on circular base, design of Turn
Buckle.
ME 312 Mechanical Machine Design is the flagship course of the mechanical engineering department at DHA Suffa University. This lecture is about mechanical fasteners and non-permanent joints. The course is offered every fall by Dr. Bilal A. Siddiqui.
,
diploma mechanical engineering
,
mechanical engineering
,
machine design
,
design of machine elements
,
knuckle joint
,
failures of knuckle joint under different streses
,
fork end
,
single eye end
,
knuckle pin
Springs - DESIGN OF MACHINE ELEMENTS-IIDr. L K Bhagi
Introduction to springs, Types and terminology of springs, Stress and deflection equations, Series and parallel connection, Design of helical springs, Design against fluctuating load, Concentric springs, Helical torsion springs, Spiral springs, Multi-leaf springs, Optimum design of helical spring
Design and Fabrication of Manual Spring Rolling MachineIJERA Editor
This paper is to discuss to design and fabrication of a manual spring rolling machine by a simple mechanism arrangement for the production of closed and open coil helical springs. This machine is operated by manual method. This machine produces closed coil helical spring of different diameter and different length. Rolling is the process of bending metal wire to a curved form. The article in the shape of round is made by spring roller shaft. Rolling operation can be done on hand or power operated rolling machine. It can make a spring from a shaft. A shaft is a rotating machine element which is used to transmit power from one place to another. A bearing is machine element which supports another moving machine element. Guider is used to guide the raw material (spring wire). This guider moves on the shaft automatically. This self-movement is achieved by the lead of spring. Handle is used to operate the rolling machine manually, without electric power frame is carries an all parts of the machine, it is made up of mild steel. A work holding mechanism is used to hold the mandrel; it is attached to the main shaft of machine. Mandrel is fitting in the work holding mechanism, the mandrel’s outer diameter is known as internal diameter of the spring.
Selection of manufacturing methods for knuckle jointViraj Dendge
In this Presentation We have discussed about 'Selection of manufacturing methods for knuckle joint '. We also made design Calculations of 'Knuckle Joint' .
Explore the innovative world of trenchless pipe repair with our comprehensive guide, "The Benefits and Techniques of Trenchless Pipe Repair." This document delves into the modern methods of repairing underground pipes without the need for extensive excavation, highlighting the numerous advantages and the latest techniques used in the industry.
Learn about the cost savings, reduced environmental impact, and minimal disruption associated with trenchless technology. Discover detailed explanations of popular techniques such as pipe bursting, cured-in-place pipe (CIPP) lining, and directional drilling. Understand how these methods can be applied to various types of infrastructure, from residential plumbing to large-scale municipal systems.
Ideal for homeowners, contractors, engineers, and anyone interested in modern plumbing solutions, this guide provides valuable insights into why trenchless pipe repair is becoming the preferred choice for pipe rehabilitation. Stay informed about the latest advancements and best practices in the field.
About
Indigenized remote control interface card suitable for MAFI system CCR equipment. Compatible for IDM8000 CCR. Backplane mounted serial and TCP/Ethernet communication module for CCR remote access. IDM 8000 CCR remote control on serial and TCP protocol.
• Remote control: Parallel or serial interface.
• Compatible with MAFI CCR system.
• Compatible with IDM8000 CCR.
• Compatible with Backplane mount serial communication.
• Compatible with commercial and Defence aviation CCR system.
• Remote control system for accessing CCR and allied system over serial or TCP.
• Indigenized local Support/presence in India.
• Easy in configuration using DIP switches.
Technical Specifications
Indigenized remote control interface card suitable for MAFI system CCR equipment. Compatible for IDM8000 CCR. Backplane mounted serial and TCP/Ethernet communication module for CCR remote access. IDM 8000 CCR remote control on serial and TCP protocol.
Key Features
Indigenized remote control interface card suitable for MAFI system CCR equipment. Compatible for IDM8000 CCR. Backplane mounted serial and TCP/Ethernet communication module for CCR remote access. IDM 8000 CCR remote control on serial and TCP protocol.
• Remote control: Parallel or serial interface
• Compatible with MAFI CCR system
• Copatiable with IDM8000 CCR
• Compatible with Backplane mount serial communication.
• Compatible with commercial and Defence aviation CCR system.
• Remote control system for accessing CCR and allied system over serial or TCP.
• Indigenized local Support/presence in India.
Application
• Remote control: Parallel or serial interface.
• Compatible with MAFI CCR system.
• Compatible with IDM8000 CCR.
• Compatible with Backplane mount serial communication.
• Compatible with commercial and Defence aviation CCR system.
• Remote control system for accessing CCR and allied system over serial or TCP.
• Indigenized local Support/presence in India.
• Easy in configuration using DIP switches.
Saudi Arabia stands as a titan in the global energy landscape, renowned for its abundant oil and gas resources. It's the largest exporter of petroleum and holds some of the world's most significant reserves. Let's delve into the top 10 oil and gas projects shaping Saudi Arabia's energy future in 2024.
Democratizing Fuzzing at Scale by Abhishek Aryaabh.arya
Presented at NUS: Fuzzing and Software Security Summer School 2024
This keynote talks about the democratization of fuzzing at scale, highlighting the collaboration between open source communities, academia, and industry to advance the field of fuzzing. It delves into the history of fuzzing, the development of scalable fuzzing platforms, and the empowerment of community-driven research. The talk will further discuss recent advancements leveraging AI/ML and offer insights into the future evolution of the fuzzing landscape.
Final project report on grocery store management system..pdfKamal Acharya
In today’s fast-changing business environment, it’s extremely important to be able to respond to client needs in the most effective and timely manner. If your customers wish to see your business online and have instant access to your products or services.
Online Grocery Store is an e-commerce website, which retails various grocery products. This project allows viewing various products available enables registered users to purchase desired products instantly using Paytm, UPI payment processor (Instant Pay) and also can place order by using Cash on Delivery (Pay Later) option. This project provides an easy access to Administrators and Managers to view orders placed using Pay Later and Instant Pay options.
In order to develop an e-commerce website, a number of Technologies must be studied and understood. These include multi-tiered architecture, server and client-side scripting techniques, implementation technologies, programming language (such as PHP, HTML, CSS, JavaScript) and MySQL relational databases. This is a project with the objective to develop a basic website where a consumer is provided with a shopping cart website and also to know about the technologies used to develop such a website.
This document will discuss each of the underlying technologies to create and implement an e- commerce website.
Welcome to WIPAC Monthly the magazine brought to you by the LinkedIn Group Water Industry Process Automation & Control.
In this month's edition, along with this month's industry news to celebrate the 13 years since the group was created we have articles including
A case study of the used of Advanced Process Control at the Wastewater Treatment works at Lleida in Spain
A look back on an article on smart wastewater networks in order to see how the industry has measured up in the interim around the adoption of Digital Transformation in the Water Industry.
Cosmetic shop management system project report.pdfKamal Acharya
Buying new cosmetic products is difficult. It can even be scary for those who have sensitive skin and are prone to skin trouble. The information needed to alleviate this problem is on the back of each product, but it's thought to interpret those ingredient lists unless you have a background in chemistry.
Instead of buying and hoping for the best, we can use data science to help us predict which products may be good fits for us. It includes various function programs to do the above mentioned tasks.
Data file handling has been effectively used in the program.
The automated cosmetic shop management system should deal with the automation of general workflow and administration process of the shop. The main processes of the system focus on customer's request where the system is able to search the most appropriate products and deliver it to the customers. It should help the employees to quickly identify the list of cosmetic product that have reached the minimum quantity and also keep a track of expired date for each cosmetic product. It should help the employees to find the rack number in which the product is placed.It is also Faster and more efficient way.
Event Management System Vb Net Project Report.pdfKamal Acharya
In present era, the scopes of information technology growing with a very fast .We do not see any are untouched from this industry. The scope of information technology has become wider includes: Business and industry. Household Business, Communication, Education, Entertainment, Science, Medicine, Engineering, Distance Learning, Weather Forecasting. Carrier Searching and so on.
My project named “Event Management System” is software that store and maintained all events coordinated in college. It also helpful to print related reports. My project will help to record the events coordinated by faculties with their Name, Event subject, date & details in an efficient & effective ways.
In my system we have to make a system by which a user can record all events coordinated by a particular faculty. In our proposed system some more featured are added which differs it from the existing system such as security.
Immunizing Image Classifiers Against Localized Adversary Attacksgerogepatton
This paper addresses the vulnerability of deep learning models, particularly convolutional neural networks
(CNN)s, to adversarial attacks and presents a proactive training technique designed to counter them. We
introduce a novel volumization algorithm, which transforms 2D images into 3D volumetric representations.
When combined with 3D convolution and deep curriculum learning optimization (CLO), itsignificantly improves
the immunity of models against localized universal attacks by up to 40%. We evaluate our proposed approach
using contemporary CNN architectures and the modified Canadian Institute for Advanced Research (CIFAR-10
and CIFAR-100) and ImageNet Large Scale Visual Recognition Challenge (ILSVRC12) datasets, showcasing
accuracy improvements over previous techniques. The results indicate that the combination of the volumetric
input and curriculum learning holds significant promise for mitigating adversarial attacks without necessitating
adversary training.
4. 4
Why Joints are Important?
• Large components cannot be produced as a
single piece
• Mechanical systems consist of many
components made of different materials
• Majority of systems fail at joints
• To facilitate operation, maintenance and
transportation
Exercise: Prepare a list of joining (assembly)
methods known to you…
6. 6
Learning Objectives
• Select appropriate screws for a given
application
• Determine the correct size of nuts and bolts
for a given loading condition
• Use standard charts to select nuts and bolts
• Design screw joints for given loading
conditions
7. 7
Introduction
• Screw joints are detachable joints fitted together by
bolts, screws, studs, and nuts
• Widely used for fastening purposes
• Use for power transmission
• Use for fine adjustments and
measurements
8. Reasons for Non-permanent Fasteners
Field assembly
Disassembly
Maintenance
Adjustment
Shigley’s Mechanical Engineering Design
Types of Nuts and bolts
https://youtu.be/dV7vkljFClA
https://youtu.be/Lz2dRA7hjlQ
Types of screws
Studs
https://www.youtube.com/watch?v=T3faDFAzCkg
10. Thread Standards and Definitions
Shigley’s Mechanical Engineering Design
Pitch – distance between
adjacent threads.
Reciprocal of threads per
inch
Major diameter – largest
diameter of thread
Minor diameter –
smallest diameter of
thread
Pitch diameter –
theoretical diameter
between major and
minor diameters, where
tooth and gap are same
width
Fig. 8–1
11. Standardization
Shigley’s Mechanical Engineering Design
• The American National (Unified) thread standard defines
basic thread geometry for uniformity and interchangeability
• American National (Unified) thread
• UN normal thread
• UNR greater root radius for fatigue applications
• Metric thread
• M series (normal thread)
• MJ series (greater root radius)
12. Standardization
Shigley’s Mechanical Engineering Design
Basic profile for metric M and MJ threads shown in Fig. 8–2
Tables 8–1 and 8–2 define basic dimensions for standard threads
Fig. 8–2
14. Tensile Stress Area
• The tensile stress area, At , is the area of an unthreaded rod
with the same tensile strength as a threaded rod.
• It is the effective area of a threaded rod to be used for stress
calculations.
• The diameter of this unthreaded rod is the average of the
pitch diameter and the minor diameter of the threaded rod.
Shigley’s Mechanical Engineering Design
18. Square and Acme Threads
Square and Acme threads are used when the threads are intended to
transmit power
Shigley’s Mechanical Engineering Design
Table 8-3 Preferred Pitches for Acme Threads
Fig. 8–3
20. Power screw
Used to change angular motion into linear motion.
Usually transmits power.
Screw jack
Lead screw of a lathe machine
Sluice gates
Hydro screw
Fly press
Bench vice
Clamps
Turnbuckle
29. Mechanics of Power Screws
Power screw
◦ Used to change angular motion into
linear motion
◦ Usually transmits power
◦ Examples include vises, presses,
jacks, lead screw on lathe
Shigley’s Mechanical Engineering Design
Fig. 8–4
30. Mechanics of Power Screws
Find expression for torque required to raise or
lower a load
Unroll one turn of a thread
Treat thread as inclined plane
Do force analysis
Raising (Lifting) the load lowering the load
31. Mechanics of Power Screws
For raising the load
For lowering the load
Shigley’s Mechanical Engineering Design
Fig. 8–6
32. Mechanics of Power Screws
Eliminate N and solve for P to raise and lower the load
Divide numerator and denominator by cosl and use relation
tanl = l /p dm
Shigley’s Mechanical Engineering Design
33. Raising and Lowering Torque
Noting that the torque is the product of the force and the mean
radius,
Shigley’s Mechanical Engineering Design
34. Motion up the plane
Shigley’s Mechanical Engineering Design
35. Motion down the plane
Shigley’s Mechanical Engineering Design
36. Self-locking Condition
If the lowering torque is negative, the load will lower itself by
causing the screw to spin without any external effort.
If the lowering torque is positive, the screw is self-locking.
Self-locking condition is p f dm > l
Noting that l / p dm = tan l, the self-locking condition can be
seen to only involve the coefficient of friction and the lead
angle.
Shigley’s Mechanical Engineering Design
37. Power Screw Efficiency
The torque needed to raise the load with no friction losses can
be found from Eq. (8–1) with f = 0.
The efficiency of the power screw is therefore
Shigley’s Mechanical Engineering Design
38. Power Screws with Acme Threads
If Acme threads are used instead of square
threads, the thread angle creates a wedging
action.
The friction components are increased.
The torque necessary to raise a load (or
tighten a screw) is found by dividing the
friction terms in Eq. (8–1) by cosa.
Shigley’s Mechanical Engineering Design
Fig. 8–7
39. Collar Friction
An additional component of
torque is often needed to
account for the friction
between a collar and the load.
Assuming the load is
concentrated at the mean
collar diameter dc
Shigley’s Mechanical Engineering Design
Fig. 8–7
40. Stresses in Body of Power Screws
Maximum nominal shear stress in torsion of the screw body
Axial stress in screw body
Shigley’s Mechanical Engineering Design
Shear Stress
Joint should be designed so that the shear load
taken by the unthreaded portion of the bolt
41. Stresses in Threads of Power Screws
Bearing stress in threads,
where nt is number of
engaged threads
Shigley’s Mechanical Engineering Design
Fig. 8–8
42. Stresses in Threads of Power Screws
Bending stress at root of thread,
Shigley’s Mechanical Engineering Design
Fig. 8–8
43. Stresses in Threads of Power Screws
Transverse shear stress at center of root
of thread,
Shigley’s Mechanical Engineering Design
Fig. 8–8
44. Stresses in Threads of Power Screws
Consider stress element at the top of the root “plane”
Obtain von Mises stress from Eq. (5–14),
Shigley’s Mechanical Engineering Design
45. Thread Deformation in Screw-Nut Combination
Power screw thread is in compression, causing elastic shortening
of screw thread pitch.
Engaging nut is in tension, causing elastic lengthening of the nut
thread pitch.
Consequently, the engaged threads cannot share the load equally.
Experiments indicate the first thread carries 38% of the load, the
second thread 25%, and the third thread 18%. The seventh
thread is free of load.
To find the largest stress in the first thread of a screw-nut
combination, use 0.38F in place of F, and set nt = 1.
Shigley’s Mechanical Engineering Design
56. Head Type of Bolts
Hexagon head bolt
◦ Usually uses nut
◦ Heavy duty
Hexagon head cap screw
◦ Thinner head
◦ Often used as screw (in
threaded hole, without nut)
Socket head cap screw
◦ Usually more precision
applications
◦ Access from the top
Machine screws
◦ Usually smaller sizes
◦ Slot or philips head common
◦ Threaded all the way
Shigley’s Mechanical Engineering Design
Fig. 8–9
Fig. 8–10
58. Hexagon-Head Bolt
Hexagon-head bolts are one of the most common for engineering
applications
Standard dimensions are included in Table A–29
W is usually about 1.5 times nominal diameter
Bolt length L is measured from below the head
Shigley’s Mechanical Engineering Design
60. Nuts
See Appendix A–31 for typical specifications
First three threads of nut carry majority of load
Localized plastic strain in the first thread is likely, so nuts should
not be re-used in critical applications.
Shigley’s Mechanical Engineering Design
End view Washer-faced,
regular
Chamfered both
sides, regular
Washer-faced,
jam nut
Chamfered
both sides,
jam nut
Fig. 8–12
61. Tension Loaded Bolted Joint
Grip length l includes
everything being compressed
by bolt preload, including
washers
Washer under head prevents
burrs at the hole from
gouging into the fillet under
the bolt head
Shigley’s Mechanical Engineering Design
Fig. 8–13
62. Pressure Vessel Head
Hex-head cap screw in
tapped hole used to fasten
cylinder head to cylinder
body
Note O-ring seal, not
affecting the stiffness of the
members within the grip
Only part of the threaded
length of the bolt contributes
to the effective grip l
Shigley’s Mechanical Engineering Design
Fig. 8–14
63. Effective Grip Length for Tapped Holes
For screw in tapped hole,
effective grip length is
Shigley’s Mechanical Engineering Design
64. Bolted Joint Stiffnesses
During bolt preload
◦ bolt is stretched
◦ members in grip are
compressed
When external load P is
applied
◦ Bolt stretches further
◦ Members in grip
uncompress some
Joint can be modeled as a
soft bolt spring in parallel
with a stiff member spring
Shigley’s Mechanical Engineering Design
Fig. 8–13
65. Bolt Stiffness
Axially loaded rod,
partly threaded and
partly unthreaded
Consider each portion as
a spring
Combine as two springs
in series
Shigley’s Mechanical Engineering Design
66. Procedure to Find Bolt Stiffness
Shigley’s Mechanical Engineering Design
67. Procedure to Find Bolt Stiffness
Shigley’s Mechanical Engineering Design
68. Procedure to Find Bolt Stiffness
Shigley’s Mechanical Engineering Design
69. Member Stiffness
Stress distribution spreads from face of
bolt head and nut
Model as a cone with top cut off
Called a frustum
Shigley’s Mechanical Engineering Design
70. Member Stiffness
Model compressed members as if they are frusta spreading
from the bolt head and nut to the midpoint of the grip
Each frustum has a half-apex angle of a
Find stiffness for frustum in compression
Shigley’s Mechanical Engineering Design
Fig. 8–15
72. Member Stiffness
With typical value of a = 30º,
Use Eq. (8–20) to find stiffness for each frustum
Combine all frusta as springs in series
Shigley’s Mechanical Engineering Design
Fig. 8–15b
73. Member Stiffness for Common Material in Grip
If the grip consists of any number of members all of the same
material, two identical frusta can be added in series. The entire
joint can be handled with one equation,
dw is the washer face diameter
Using standard washer face diameter of 1.5d, and with a = 30º,
Shigley’s Mechanical Engineering Design
82. Bolt Materials
Grades specify material, heat treatment, strengths
◦ Table 8–9 for SAE grades
◦ Table 8–10 for ASTM designations
◦ Table 8–11 for metric property class
Grades should be marked on head of bolt
Shigley’s Mechanical Engineering Design
83. Bolt Materials
Proof load is the maximum load that
a bolt can withstand without
acquiring a permanent set
Proof strength is the quotient of proof
load and tensile-stress area
◦ Corresponds to proportional limit
◦ Slightly lower than yield strength
◦ Typically used for static strength of
bolt
Good bolt materials have stress-strain
curve that continues to rise to fracture
Shigley’s Mechanical Engineering Design
Fig. 8–18
87. Bolt Specification
Shigley’s Mechanical Engineering Design
Nominal diameter
¼-20 x ¾ in UNC-2 Grade 5 Hex head bolt
Threads per inch
length
Thread series
Class fit
Material grade
Head type
M12 x 1.75 ISO 4.8 Hex head bolt
Metric
Nominal diameter
Pitch
Material class
89. Tension Loaded Bolted Joints
During bolt preload
◦ bolt is stretched
◦ members in grip are compressed
When external load P is applied
◦ Bolt stretches an additional
amount d
◦ Members in grip uncompress same
amount d
Shigley’s Mechanical Engineering Design
Fig. 8–13
90. Stiffness Constant
Since P = Pb + Pm,
C is defined as the stiffness constant of the joint
C indicates the proportion of external load P that the bolt will
carry. A good design target is around 0.2.
Shigley’s Mechanical Engineering Design
91. Bolt and Member Loads
The resultant bolt load is
The resultant load on the members is
These results are only valid if the load on the members remains
negative, indicating the members stay in compression.
Shigley’s Mechanical Engineering Design
92. Relating Bolt Torque to Bolt Tension
Best way to measure bolt preload is by relating measured bolt
elongation and calculated stiffness
Usually, measuring bolt elongation is not practical
Measuring applied torque is common, using a torque wrench
Need to find relation between applied torque and bolt preload
Shigley’s Mechanical Engineering Design
93. Relating Bolt Torque to Bolt Tension
From the power screw equations, Eqs. (8–5) and (8–6), we get
Applying tanl = l/pdm,
Assuming a washer face diameter of 1.5d, the collar diameter is
dc = (d + 1.5d)/2 = 1.25d, giving
Shigley’s Mechanical Engineering Design
94. Relating Bolt Torque to Bolt Tension
Define term in brackets as torque coefficient K
Shigley’s Mechanical Engineering Design
95. Typical Values for Torque Coefficient K
Some recommended values for K for various bolt finishes is
given in Table 8–15
Use K = 0.2 for other cases
Shigley’s Mechanical Engineering Design
96. Distribution of Preload vs Torque
Measured preloads for 20 tests at same torque have considerable
variation
◦ Mean value of 34.3 kN
◦ Standard deviation of 4.91
Shigley’s Mechanical Engineering Design
Table 8–13
97. Distribution of Preload vs Torque
Same test with lubricated bolts
◦ Mean value of 34.18 kN (unlubricated 34.3 kN)
◦ Standard deviation of 2.88 kN (unlubricated 4.91 kN)
Lubrication made little change to average preload vs torque
Lubrication significantly reduces the standard deviation of
preload vs torque
Shigley’s Mechanical Engineering Design
Table 8–14
108. Gasketed Joints
For a full gasket compressed between members of a bolted
joint, the gasket pressure p is found by dividing the force in the
member by the gasket area per bolt.
The force in the member, including a load factor n,
Thus the gasket pressure is
Shigley’s Mechanical Engineering Design
109. Gasketed Joints
Uniformity of pressure on the gasket is important
Adjacent bolts should no more than six nominal diameters apart
on the bolt circle
For wrench clearance, bolts should be at least three diameters
apart
This gives a rough rule for bolt spacing around a bolt circle of
diameter Db
Shigley’s Mechanical Engineering Design
110. Fatigue Loading of Tension Joints
Fatigue methods of Ch. 6 are directly applicable
Distribution of typical bolt failures is
◦ 15% under the head
◦ 20% at the end of the thread
◦ 65% in the thread at the nut face
Fatigue stress-concentration factors for threads and fillet are
given in Table 8–16
Shigley’s Mechanical Engineering Design
111. Endurance Strength for Bolts
Bolts are standardized, so endurance strengths are known by
experimentation, including all modifiers. See Table 8–17.
Fatigue stress-concentration factor Kf is also included as a
reducer of the endurance strength, so it should not be applied to
the bolt stresses.
Ch. 6 methods can be used for cut threads.
Shigley’s Mechanical Engineering Design
112. Fatigue Stresses
With an external load on a per bolt basis fluctuating between Pmin
and Pmax,
Shigley’s Mechanical Engineering Design
113. Typical Fatigue Load Line for Bolts
Typical load line starts from constant preload, then increases
with a constant slope
Shigley’s Mechanical Engineering Design
Fig. 8–20
114. Typical Fatigue Load Line for Bolts
Equation of load line:
Equation of Goodman line:
Solving (a) and (b) for intersection point,
Shigley’s Mechanical Engineering Design
Fig. 8–20
115. Fatigue Factor of Safety
Fatigue factor of safety based on Goodman line and constant
preload load line,
Other failure curves can be used, following the same approach.
Shigley’s Mechanical Engineering Design
116. Repeated Load Special Case
Bolted joints often experience repeated load, where external load
fluctuates between 0 and Pmax
Setting Pmin = 0 in Eqs. (8-35) and (8-36),
With constant preload load line,
Load line has slope of unity for repeated load case
Shigley’s Mechanical Engineering Design
117. Repeated Load Special Case
Intersect load line equation with failure curves to get
intersection coordinate Sa
Divide Sa by sa to get fatigue factor of safety for repeated load
case for each failure curve.
Shigley’s Mechanical Engineering Design
Load line:
Goodman:
Gerber:
ASME-elliptic:
118. Repeated Load Special Case
Fatigue factor of safety equations for repeated loading, constant
preload load line, with various failure curves:
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Goodman:
Gerber:
ASME-elliptic:
119. Further Reductions for Goodman
For convenience, sa and si can be substituted into any of the
fatigue factor of safety equations.
Doing so for the Goodman criteria in Eq. (8–45),
If there is no preload, C = 1 and Fi = 0, resulting in
Preload is beneficial for resisting fatigue when nf / nf0 is greater
than unity. This puts an upper bound on the preload,
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120. Yield Check with Fatigue Stresses
As always, static yielding must be checked.
In fatigue loading situations, since sa and sm are already
calculated, it may be convenient to check yielding with
This is equivalent to the yielding factor of safety from Eq. (8–28).
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130. 130
Locking Devices for Screw Joints
The basic principles used in locking devices
▪ The increase of friction forces between the contact
surfaces
▪ The application of special stops such as split pins
▪ The use of permanent locks such as welding and
punching
132. Bolted and Riveted Joints Loaded in Shear
Shear loaded joints are
handled the same for
rivets, bolts, and pins
Several failure modes are
possible
(a) Joint loaded in shear
(b) Bending of bolt or
members
(c) Shear of bolt
(d) Tensile failure of
members
(e) Bearing stress on bolt
or members
(f) Shear tear-out
(g) Tensile tear-out
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Fig. 8–23
133. Failure by Bending
Bending moment is approximately M = Ft / 2, where t is the
grip length, i.e. the total thickness of the connected parts.
Bending stress is determined by regular mechanics of materials
approach, where I/c is for the weakest member or for the
bolt(s).
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134. Failure by Shear of Bolt
Simple direct shear
Use the total cross sectional area of bolts that are carrying the
load.
For bolts, determine whether the shear is across the nominal
area or across threaded area. Use area based on nominal
diameter or minor diameter, as appropriate.
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135. Failure by Tensile Rupture of Member
Simple tensile failure
Use the smallest net area of the member, with holes removed
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136. Failure by Bearing Stress
Failure by crushing known as bearing stress
Bolt or member with lowest strength will crush first
Load distribution on cylindrical surface is non-trivial
Customary to assume uniform distribution over projected
contact area, A = td
t is the thickness of the thinnest plate and d is the bolt diameter
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137. Failure by Shear-out or Tear-out
Edge shear-out or tear-out is avoided by spacing bolts at least
1.5 diameters away from the edge
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144. Shear Joints with Eccentric Loading
Eccentric loading is when the load does not pass along a line of
symmetry of the fasteners.
Requires finding moment about centroid of bolt pattern
Centroid location
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Fig. 8–27a
145. Shear Joints with Eccentric Loading
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(a) Example of eccentric
loading
(b) Free body diagram
(c) Close up of bolt pattern
Fig. 8–27
146. Shear Joints with Eccentric Loading
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Primary Shear
Secondary Shear, due to moment
load around centroid